Thermal management is an issue for packaging, for example, power modules, and high power semiconductors, because use of power devices can lead to losses which generate heat. Heat generated at dies can be extracted through a heat sink. The modules can be mounted on the heat sink and heat can flow through an internal structure of the module through a base plate to the heat sink. The base plate can be a contributor to thermal resistance. Therefore, optimization and reduction of the heat resistance of the base plate can have an impact on the thermal management and the reliability and lifetime of, for example, a power module and a high power semiconductor.
EP 2 012 354 A1 discloses a base plate for a power module including an aluminium silicon carbide composite and aluminium layers made of a metal containing aluminium as the main component formed on respective principal planes of the aluminium silicon carbide composite. In order to reduce a gap between the base plate and a heat-dissipation fin, or heat sink, respectively, the base plate is formed to have a convex bow.
EP 1 973 157 A1 discloses a base plate for a power module including an aluminium silicon carbide composite that is a flat plate-shaped silicon carbide porous body impregnated with a metal containing aluminium as the main component, and an aluminium layer made of a metal containing aluminium as the main component formed only on one of the principal planes of the aluminium silicon carbide composite. The base plate is formed to have a convex bow in order to reduce a gap between the base plate and a heat-dissipation fin, or heat sink, respectively.
These base plates have limited ability to be adapted to topography, or roughness, respectively, of a surface of the heat sink. This can lead to formation of voluminous cavities between the base plate and the surface of the heat sink, thereby reducing heat-dissipation properties. These base plates can be secured to the internal structure of the power module as well as to the heat sink with internal tension in order to get sufficient heat-dissipation properties. Consequently, there can be a risk of the base plate to crack.
Proceedings PCIM Europe 2009 Conference, Ayumi Maruta, Mitsuharu Tabata, 2500 A/1200V Dual IGBT Module, discloses a layout of a power module which includes a cooling fin on which a plurality of separated base plates, or base plate sections, respectively, are arranged.
Where a base plate is joined with a heat sink, a heat dissipation grease, gel, or mat, having high thermal conductivity can be applied to portions to be joined. The base plate can be fixed to the heat sink, or a heat-dissipation unit, respectively by screws through holes provided in a peripheral portion of the base plate. In the layout described above, the formation of gaps between the respective base plates may not be completely avoided. These gap-formations can lead to a leakage of the grease through the gaps. The materials, such as low molecular weight molecules of the gel, other particles, or the like can diffuse from the inside of the module to the outside. A loss of grease can reduce heat dissipation from the base plate to the heat sink.